Are you killing him off because the story calls for it, or because you hate managing six-person groups, as you said? If it is more the latter then the former, maybe consider a practice run, in a different document, practicing writing your group. Just write out a scene with the six characters together, having fun (or doing whatever you want - doesn’t matter). Get yourself more comfortable with managing so many characters. Then keep the character.
But if you are killing the character because the story calls for it above anything else, you have to just do it. If you are sad - a perfectly valid emotion for you to have; you did create this character after all - I think it’s likely that you wrote him well, and readers will feel the death and the loss the other characters feel.
If it helps, I killed off my main POV character in one of my stories. It was very difficult, especially when I first realized before I even got to the end of the story that I needed to do it (it’s a trilogy - I was halfway through book two when I realized it). It messed me up for three weeks, trying to fight the thoughts of his death and figure out a way that I could let him live. But I did it; he died. And I know it’s the right thing for the story, even if I still, a good six months after writing his death, miss him and wish he had a better ending.